Ensure VALID response from fcU updates protoarray (#3126)

## Issue Addressed

NA

## Proposed Changes

Ensures that a `VALID` response from a `forkchoiceUpdate` call will update that block in `ProtoArray`.

I also had to modify the mock execution engine so it wouldn't return valid when all payloads were supposed to be some other static value.

## Additional Info

NA

beacon_node/execution_layer/src/test_utils/handle_rpc.rs

@@ -100,7 +100,9 @@ pub async fn handle_rpc<T: EthSpec>(
             let forkchoice_state: JsonForkChoiceStateV1 = get_param(params, 0)?;
             let payload_attributes: Option<JsonPayloadAttributesV1> = get_param(params, 1)?;
 
-            let response = ctx
+            let head_block_hash = forkchoice_state.head_block_hash;
+
+            let mut response = ctx
                 .execution_block_generator
                 .write()
                 .forkchoice_updated_v1(
@@ -108,6 +110,14 @@ pub async fn handle_rpc<T: EthSpec>(
                     payload_attributes.map(|json| json.into()),
                 )?;
 
+            if let Some(mut status) = ctx.static_forkchoice_updated_response.lock().clone() {
+                if status.status == PayloadStatusV1Status::Valid {
+                    status.latest_valid_hash = Some(head_block_hash)
+                }
+
+                response.payload_status = status.into();
+            }
+
             Ok(serde_json::to_value(response).unwrap())
         }
         other => Err(format!(